This will do a single SQL query to get all organizations by ids 1,4, and 9. You
can load multiple batches from multiple sources, and then when run/1 is called
batch will be loaded concurrently.

Here we named the source :db within our dataloader. More commonly though if
you're using Phoenix you'll want to name it after one of your contexts, and have
a different source used for each context. This provides an easy way to enforce
data access rules within each context. See the DataLoader.Ecto moduledocs for
more details

Sources

Dataloader ships with two different built in sources. The first is the Ecto source for easily pulling out data with ecto. The other is a simple KV key value source. See each module for its respective documentation.

Anything that implements the Dataloader.Source protocol can act as a source.